Apparatus for electromagnetic separation of wet ores



Dec. 25 1953 A. 1.. J. QUENEAU APPARATUS FOR ELECTROMAGNETIC SEPARATION OF WET ORES Filed Sept. 9, 1950 lllllllllllllilllll lilllllllllllllll FIG. 2

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INVENTOR usfm L. J Our/read W ATTORNEYS than the previously described types.

Patented Dec. 29, 1953 UNITED STATES PATENT OFFICE APPARATUS FOR ELECTROMAGNETIC SEPARATION OF WET ORES Augustin L. J. Queneau, Morristown, N. J.

Application September 9, 1950, Serial No. 184,000

1 Claim.

Large bodies of iron ores in the form of hem-- T atite, limonite and the like are available, in which iron oxide is mixed with such quantities of silica, silicates and other gangue materials as to make the direct smelting of such ores in a blast furnace uneconomical. Owing to the rapid exhaustion of the known beds of high gradeiron ores, the iron and steel industry will, in the near future, depend upon the supply of lower grade ores. This necessitates the provision of economical means for separating the values from the gangue materials. Because of the relatively low magnetic susceptibility of the metallic values in some ores, the separation is not easy to accomplish. Hematite, for example, has a very low magnetic susceptibility, and it cannot be separated magnetically by conventional .dry magnetic separators on a commercial basis.

I have heretofore developed methods of and apparatus whereby the separation of mineral values of low magnetic susceptibility can be accomplished as shown, for example, in Letters Patent Nos. 2,088,364, 2,154,010, 2,258,194. an 2,290,892. In the patented apparatus, the ore, in the form of a pulp with water, is caused to flow at a constant hydrostatic head past rotating poles which attract and divert the magnetically susceptible material from the path of flow of the pulp and thus deliver valuable portions of the ore into containers separate from the gangue materials. In Patent No. 2,258,194, I have described a duplex separator in which the flowing material is subjected to the action of two concentrated magnetic fields successively to efiect a more complete separation of values from the gangue.

In an application Ser. No. 784,804 filed November 8, 1947, now abandoned, I have described a quadruplex separator which is more efiicient The latter separator is particularly useful with ores containing relatively low proportions of materials such as magnetite which has a high magnetic susceptibility. If upward of a few per cents of magnetite are present in the pulp, the magnetite must first be removed by subjecting the pulp to a low intensity separation. Otherwise it would cause bridging across the rotating poles of the separator and prevent the flow of the pulp therethrough. This entails two operations in sheet.- ing separation of the values Irom the gangue.

in an appllcation :ser. No. 118,455 riled August 15,v 19b0, 1 have escribed an improved method and apparatus in which ores containing substantial proportions of magnetite may be sub ected to a single operation. The tendency of the more readily separated magnetite to bridge the now passage between the magnetic poles being prevented by successively and alternately increasing and decreaslng the neld strength adjacent the opposlte sides of the now passage so as to alternately urge the. magnetic particles attracted to one side or the flow passage and then to the other side of that passage downwardly and laterally away from the main how or the pulp while leaving the magnetic partlcles attracted to the opposite side of the passage in place and uh.- allected or to some extent less strongly attracted, in this way facilitating the separation of any untrapped gangue particles from the particles collected on that opposite side of the passage. In the intervals when the field strength is increased at such opposite side of the passage, then again is reversed, the particles that have collected on that side then being positively urged downwardly and laterally away irom the main flow. The present invention involves an improvement. in the rotating poles adapted to cause the successive and alternate increase and decrease in the effective field strength adjacent the respective sides of the fiow passage.

It is the object or the present invention, therefore, to provide an improved a paratus capable of performing the method as described in my application Ser. No. 109,458 aforesaid, and therefore suitable. for separating mineral values from orepulps in which values of high magnetic susceptibillty such as magnetite as well as those of lower magnetic susceptibility such as hematite, limonite, goethit and the like are also present, the separation being accomplished in a single operation.

Other objects and advantages of the invention will be apparentv as it is better understood by reference to the following specification and the accompanying drawings, in which Fig. 1 is an elevation partially in section of an apparatus embodying my invention;

Fig. 2 is an enlarged sectional view of the improved rotating poles; and

Fig. 8 is a transverse section through the structure shown in Fig. 2.

In accordance with the principles of the invention, the magnetic field is established by the provision of cores which are suitably wound with a multiplicity of coils of wire adapted to be supplied from any suitable source of direct current. The cores are connected by a yoke to complete the magnetic circuit except for the gap between the cores. As described in my application Ser. No. 179,458, it may be desirable, in order to permit further modification of the magnetic intensity at different levels of the separator, to provide two such yokes with corresponding cores and coils. By varying the number of turns of wire on the cores, the desired intensity of the magnetic fields can be obtained. Polar extensions are connected to the cores to afford a relatively long vertical gap. Between the extensions, a separator box is disposed through which the pulp flows. The pulp is supplied at the top. The bottom outlet of the separator box has a restricted opening and an overflow is provided at the top so that a constant hydrostatic head is maintained in the downwardly flowing pulp as described in the patents heretofore mentioned.

The walls of the separator box have semicylindrical recesses formed therein in opposed relationship on opposite sides of the box. In each recess a rotating member is mounted on a suitable shaft. The shafts are driven so that all the pole members on one side rotate in a clockwise direction, and those on the other side rotate in a counter-clockwise direction. The surface of each pole member is provided with projecting teeth preferably equidistantly spaced from one another. In accordance with the present invention, the revolving pole members have a cross-section conforming to an eccentric conic section, for example, an ellipse. They are so mounted and rotate in a manner such that the major cross-sectional axis of one pole is always perpendicular to the minor cross-sectional axis of the other pole during successive phases of rotation. Each semi-cylindrical recess is preferably formed as the arc of a circle having a radius only slightly larger than one-half the length of the major cross-sectional axis of the rotating pole member intended to be mounted for rotation therein. It will thus be seen that as each pole rotates the effective gap between the adjacent surfaces of the poles mounted in the opposed recesses remains substantially constant. However, the fiux intensity constantly varies from one side to the other of the throat area between the opposed recesses due to the fact that the rotating poles alternately approach and recede from the throat area. The variation of the flux intensity is further enhanced at periodic intervals in the rotation of the poles by reason of the fact that when each pole is in a position in which its major cross-sectional axis lies in the plane of the axes of the opposed poles it presents a relatively reduced area at the gap between it and the opposed pole which at that moment presents a relatively extended surface facing the throat area. Consequently the lines of force across the gap are more concentrated at the reduced area of the pole that is closer to the throat area and the tendency of that pole to attract magnetically susceptible particles to it will be correspondingly increased.

Since the magnetic attraction of the poles for the magnetically susceptible particles varies as the square of the distance of such poles from the particles, it will be understood that as the poles of elliptical cross-section are rotated there is an alternating increase and decrease of the magnetic pull or attraction on the particles toward the pole on the one side and then toward the pole on the other side of the throat defined between the arcuate passages. Furthermore, as one of the two opposite edge surfaces that are bisected by the major cross-sectional axis of the pole piece travels downwardly past the throat area it brings the magnetically susceptible particles collected on the adjacent wall of the arcuate recess under the influence of the relatively high field strength of that pole and acts to urge the collected particles downwardly and laterally away from the main downwardly flowing current of the pulp to a point of collection.

I have discovered that the use of rotating poles of the type described avoids completely the bridging diificulty which is experienced when materials containing a substantial proportion of iron oxide having high magnetic susceptibility such as magnetite are included in the pulp. The rotating poles may be made from sheets of low metalloid steel alternating with sheets of Zinc, although they may be made also of solid low metalloid steel in the prescribed form.

The particles of values which are drawn toward the rotating poles are directed past barriers which separate them from the mass of pulp flowing downwardly through the box and thence into pipes at the side of the separator, and are thus removed. Two such barriers may be used at each point of separation so that I may secure concentrates, middlings and tailings from the separator. The tailings are delivered substantially free from values and consist of the gangue materials in the pulp. During the passage of the material through the separating path, it is subject continuously to the stray magnetic field, and hence the susceptible particles do not lose polarity. This materially assists the defiection of the suspended particles as they enter the successive concentrated fields.

Inasmuch as the present invention relates particularly to the form of the rotating poles, it is unnecessary to describe the entire apparatus as shown and described in my application Ser. No. 179,458. It is to be understood that the rotating poles constructed in accordance with the present invention may be substituted for those described and shown in the earlier application. It will suffice to describe the improved rotating poles in connection with the uppermost of the rotating poles as in the earlier application. They are preferably of laminated construction, the laminations consisting of alternate sheets of low metalloid steel and of zinc. The thickness of the sheets may be, for example, .075 inch. Such rotating poles are extremely desirable Where any substantial amount of magnetite is present in the pulp, since they prevent bridging of the magnetite. The rotating poles beneath the first set may be duplicates of the first set or they may be of any other suitable construction.

Referring to the drawings, 5 indicates a separator box which is supported in any suitable manner. Inlet pipes 6 permit the introduction of the pulp. The pipes have openings 1 below the upper surface of the pulp which is maintained by a weir 8 connected to an overflow pipe 9. At the bottom of the separator box, an outlet I9 is provided with a diaphragm ll having an opening l2 of restricted size to limit the flow of pulp through the separator box, thus maintaining a uniform hydrostatic head in the flowing pulp.

The sides of the separatorbox are provided with a plurality of arcuate recesses on each side thereof, one of the recesses being shown atl3 in Fig. 1. are mounted on shafts I8, which are suitably journaled in frame members 22 and 23. The shafts is are driven from any suitable source of power by gears and pinions (not shown) or other suitable means, so that the shafts on opposite sides of the separator box are driven in opposite directions, clockwise on one side and counterclockwise on the other.

Beneath each of the arcuate recesses l3, upwardly directed partitions 2:2 and 25 are provided with their edges spaced from the wall of the separator box so that as the particles of magnetically susceptible material are drawn inwardly toward the inner side of the arcuate recess, they are directed behind the partition 24. The more magnetically susceptible material passes behind the partition 25, thus immediately separating concentrates and middlings from the pulp passing downwardly through the separator box. As the magentic flux decreases, the concentrates and middlings are released while the pulp continues to flow downwardly into the zone or the next succeeding rotating poles which separate additional particles similarly from the pulp.

In order to supply the magnetic flux, cores 2*? are connected to a yoke 2'! and carry coils '28 which are connected to a suitable source of direct current. The magnetic circuit is closed through the yoke 2! except for the gaps between the polar extensions 29 which are secured to the cores 2%. The polar extensions 29 extend upwardly along the edges of the separator box 5 and are provided with a plurality of arcuate recesses es in which the several rotating poles operate. As already indicated, twin sets of cores yokes El and coils 28 may be provided and connected to separate sources of power, the windings of the coils being varied so that the upper most set affords a lower magnetic flux than the lower set. The faces of the polar extensions 29 adjacent the sides of the separator box 5 are preferably grooved to provide a plurality of projections affording a plurality of concentrated magnetic fields extending through the path of travel of the pulp as it descends in the box. These concentrated fields have the eifect of diverting the magnetically susceptible particles toward the sides of the separator box so that they pass readily into the zones of maximum magnetic intensity provided by the rotating poles i l to H inclusive. Consequently the operating efficiency of the rotating poles is increased, and maximum separation is easily obtained.

Referring particularly to Figs. 2 and 3, the form of the rotating poles particularly at the upper zones of the separator will be readily understood. The poles M, for example, are preferably formed with laminations consisting of alternate sheets of low metalloid steel and zinc, the thickness of the sheets being usually .075 inch. The poles have the form preferably of an ellipsoid, that is to say, the cross-section is illiptical, although the cross-section may be varied to conform to any eccentric conic section. As shown in Fig. 2, the opposing rotating poles M are out of phase, so that the major cross-sectional axis of one pole is perpendicular to the minor cross sectional axis of the other during successive phases of rotation, thus affording the maximum and minimum gap in the path of the magnetic flux at the plane of desired separation. As the poles rotate, there is a constant variation in the In these recesses, rotating poles I4 flux between a maximum and a minimum, and

it has been found that the use of poles of this particular type will permit the separation of particles of high magnetic susceptibility such as magnetitefrom the pulp without danger of bridging, even though the proportion of magnetite in the pulp may be relatively high, that is, 30% or more.

The successive sets of rotating poles may be of similar form and construction. However, it is desirable to increase the strength of the flux as the pulp descends, and in the second set of poles the laminations of low metalloid steel and of zinc may be of different thickness, the former being- .075 inch thick, and the latter .050 inch thick, thus providing a greater cross-section of ferrous metal for the magnetic flux than in the first pair of rotating poles. The third set of rotating poles may be of similar form to the first two, but are preferably made of solid low metalloid steel. The fourth set of rotating poles are preferably of full cylindrical section, as disclosed in my application Ser. No. 284,804, now abandoned, with teeth on the periphery.

It will be understood that the cores 25 carrying the coils 28 of wire should be of steel of relatively high magnetic permeability so as to afford the maximum concentration of the magnetic flux at the desired points for the current consumed. The shafts upon which the rotatable poles are mounted should be made of stainless steel or other non-magnetic material of suitable strength to withstand the powerful force of the magnetic field which tends to distort the shafts. The separator box 5 and its appurtenant parts must be of non-magnetic material such as brass, aluminum and the like, in order that the magnetic flux may function properly to draw the magnetically susceptible particles into the desired channels and thus separate them from the pulp.

As in the case of separators described in my earlier Patent No. 2,290,892, it is necessary to provide outlets for the separated materials which will ensure maintenance of the desired height of liquid in the separator box. I may employ in connection with these outlets the means disclosed in Fig. 2 of Patent No. 2,290,892 or any other similar means adapted to accomplish the function. As the particles of magnetically susceptible material are withdrawn from the pulp, they dis place water of equal volume, causing the current of water to flow outward past the edges of the partitions 24 and 25 into the downwardly moving pulp stream, thus tending to prevent the entrance of non-magnetic particles into the stream of concentrates which are continuously separated from the pulp stream.

The method and apparatus as described have been successfully used in practical operation and ensure the maximum eifective separation of the values from the ores with the minimum of equipment and power consumption. They are applicable particularly to ores consisting of mixtures of magnetite and hematite and the like, with the percentages of magnetite of 39% and over. Although I prefer the laminated structure for the rotatable poles as described, similar rotating poles of solid construction may be employed with ores in which hematite is largely dominant. By subjecting the pulp successively to a magnetic flux of progressively increasing intensity in the man ner described, substantially all of the values are removed by the effect of the three upper sets of rotating poles. Any remaining values are separated by the lowermost set of rotating poles, and

the gangue is delivered substantially free from values.

Various changes may be made in the details of the procedure and in the apparatus as described without departing from the invention or sacrificing the advantages thereof.

I claim:

In an apparatus for the wet electromagnetic separation of materials consisting of mixtures of magnetically susceptible materials varying substantially in their magnetic susceptibilities such as mixtures of magnetite and hematite, a vertically extending separator box provided with enclosing side and bottom walls for receiving and maintaining a liquid suspension of such material under a controlled hydrostatic head, means defining a restricted discharge opening in the bottom portion thereof through which to maintain a controlled discharge of residue of said liquid suspension, said box having opposite side wall portions provided with opposed inwardly extending arcuate recesses defining between them a narrow throat, an electromagnet including rotatable pole pieces of substantially elliptical crosssection disposed within said opposed recesses and cooperating to maintain a magnetic field throughout the expanse of said throat, said r0- tatable poles being positioned substantially 90 out of phase with respect to each other so that as they rotate the major axis of the elliptical cross-section of one pole passes through the plane of the axes of the poles simultaneously with the minor axis of the elliptical cross-section of the other pole, said poles being effective to increase the field intensity alternately at one and then the other side of said throat while simultaneously decreasing the field intensity at the opposite side thereof, thereby urging magnetic particles attracted to the side of the recess disposed within said field of increased intensity along said side downwardly and laterally away from said throat, and means providing a separate discharge passage for attracted particles that are moved laterally away from said throat.

AUGUSTIN L. J. QUENEAU.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 910,664 Green Jan. 26, 1909 2,188,515 Payne Jan. 30, 1940 2,258,194 Queneau Oct. '7, 1941 FOREIGN PATENTS Number Country Date 20,545 Great Britain of 1906 

